I just bought a HP Pavillion p6234f desktop computer with windows 7 64bit. It has one expansion PCI slot and one expansion AGP slot.
In the AGP slot I have: GeForce 9400GT card. Which works great with 2 monitors. No problems.
Today, I tried installing a VisionTek X1300 256MB dual card to hook up my 3rd monitor. When it's installed windows takes foreverrrrrr to load up and then when it finally gets into windows, it only lets me use 1 monitor. The other 2 monitors are not seen.
Then, I tried removing the GeForce and having only the VisionTek, hooked up 2 monitors to it and it booted into windows fine, and worked... except it didn't "extend" to the 2nd monitor. Instead, it duplicated the first monitor, and there was no place to select the option to "extend" instead of "duplicate".